1. Field of the Invention
This invention relates to a board clamp made of a plastic material and designed to fulfill a variety of useful purposes such as of fastening various component parts to a body of an automobile, a chassis of an electric appliance or the like, and particularly, steadily clamping two boards or panels.
2. Description of the Prior Art
A variety of panel-to-panel clamping devices so-called "board clamps" made of a plastic material are used in automobiles and electric appliances. The board clamps have various shapes in accordance with the forms of objects such as panel-like parts or articles to be fastened, but each fundamentally comprises a head member which is larger in diameter than a fitting hole formed in a board or panel, and a leg member extending downward from the head member so as to be fitted into the fitting hole. The head member generally has hooking means or a flange or other specific shape so as to be engaged with one of the objects to be clamped together. The leg member has a generally somewhat larger outer diameter than the fitting hole formed in the other object to be fastened so as not to come out of the fitting hole. With the clamping devices of this type, two boards or any other articles can be steadily clamped to each other with a simple operation.
For example, Japanese Utility Model Applications Nos. SHO 64-17014, HEI 2-60707, HEI 3-113108 and HEI 3-117114 suggest board clamps each comprising an anchor-shaped leg having a pair of engaging pieces inclined upward from the lower end of an axial stem. Also, in Japanese Utility Model Application No. SHO 63-154808, there is proposed a board clamp having stem-less engaging legs. In addition, Japanese Utility Model Appln. No. SHO 63-115903 discloses a clip having one or more leg members formed of a corrugated plate.
All of these conventional board clamps have been designed dependent on the shape of a molding die used in plastic injecting molding. That is, the former four board clamps each are featured by the side engaging pieces laterally protruding in the opposite directions from the axial stem, but no engaging piece is disposed on the front and rear sides. On the other hand, the board clamp of Japanese U. M. Appln. No. SHO 63-154808 as noted above possesses no stem along the axial center of the engaging legs arranged in a circle because of technical reasons in the plastic injection molding no matter that the stem is necessary. The corrugated leg member in the clip of Japanese U. M. Appln. No. SHO 63-115908 is designed so as to be fitted as tight as possible into a fitting hole formed in a board or panel, but a stem is also not provided in this conventional clip.
Discussing a few points about the aforementioned prior art clamps, the board clamp having the anchor-shaped leg cannot withstand a load which is applied thereto in the direction perpendicular to the directions in which the engaging pieces protrude oppositely from the axial stem, and thus, will be easily slackened or will cease to function due to a shock, vibration or any other possible cause.
The board clamp comprising the stem-less engaging legs insufficiently retains a plate-like object in position, and therefore, will possibly be slackened or ruined when being subjected a relatively large load.
Considering the existing technique of plastic injection molding, it will be difficult to all together eliminate these drawbacks suffered by the conventional board clamps.
Further, there has been another board clamp having a hollow engaging leg of a plastic material to utilize its elasticity to be elastically fitted into a fitting hole bored in a board or panel. The hollow engaging leg is first retracted resiliently inward when being inserted into the fitting hole in the board, and resumes its original shape when being completely fitted in the fitting hole. This board clamp is easy to handle, providing advantageous uniting of the boards.
However, the board clamp utilizing the elasticity of the plastic hollow engaging leg in being inserted into the fitting hole in the board is not quite rigid, and thus, it cannot steadily retain the boards or the like in position. Although the board clamp may be successfully fitted into the fitting hole when perpendicularly inserting the elastic engaging leg through the center of the fitting hole in the board, the elastic engaging leg will be deformed or broken when being inserted slantwise into the fitting hole or coming in touch with the edge of the fitting hole during the inserting. As a result, the board clamp may possibly be deprived of its function. This disadvantage becomes particularly conspicuous when a board or other possible article is secured to a fundamental substrate with a plurality of clamps of this type. The case in which a trim board as an upholstery plate is anchored to the inside of a car door is one example entailing such a disadvantage. That is, when the trim board is fixed onto the inside of the car door, in general, a number of the board clamps are previously attached to the back side of the trim board at prescribed intervals, and then, fitted into corresponding fitting holes formed in the inside of the car door at one time while bringing the trim board in a face-to-face union with the car door. However, at this time, the clamps often fail to be fitted into the fitting holes due to the inequality of the positions on the trim board to which the clamps are attached and an error in measurement in making the fitting holes.
Not infrequently, there are times when the trim board is incompletely mounted on the car door, because it is difficult to visually inspect the condition of the attachment of the board clamps interposed between the trim board and car door.